This PhD thesis is situated in the field of work and organizational psychology and focuses on subordinate perspectives of leader competence and incompetence. Many organizations rely on leaders to lead subordinates toward effectiveness. However, leaders are not always competent and/or they are perceived as incompetent by their subordinates. Leader incompetence has negative but also positive effects on subordinates. One main goal of my thesis was to investigate the subordinate's perceptions and behaviors toward an incompetent leader. Also, I was interested in the potential consequences of leader incompetence on different outcomes, such as subordinate satisfaction and dydic performance. I concentrated on two main types of (in)competence: task (in)competence and interpersonal (in)competence. To study these topics, I conducted five lab studies (three articles) mainly simulating leader-subordinate interactions on a problem-solving task. Results revealed not only negative but also positive impacts of leader (in)competence. Theoretical implications as well as future research directions are discussed. Finally, main applied implications and practical advice are suggested.